Further studies on extracts of vitreous from several species are planned with chemical purification and characterization of the active factors in adult vitreous that have the inhibitory quality against neovascularization. The primary assays will be the fetal endothelial cell culture utilizing tritiated thymidine and cell counts and the chick chorioallantoic membrane. With further purification the material will be tested against the experimental model of retinal neovascularization induced in the young animal by oxygen.